The incursion was the second time since the end of World War II that a Chinese military ship entered Japanese waters.

A Chinese observation ship also shadowed the US aircraft carrier John C. Stennis in the Western Pacific, as it joined warships from Japan and India for drills close to waters Beijing considers its backyard.

China’s Defense Ministry said in a brief statement that the ship sailed through “a territorial strait open to international navigation” in accordance with freedom of navigation under the UN Convention on the Law of the Sea.